中高煤阶煤层煤体结构识别测井法适用性评价研究

Applicability evaluation of logging method for recognition of coal body structure in medium and high rank coal seams

煤体结构对煤储层渗透率有重要影响,渗透率是煤层气勘探开发中的一个核心参数,而测井方法在大量煤层气区块煤体结构识别中得到应用,但尚处于探索阶段。分析研究了前人在不同煤层气区块煤体结构识别中使用的测井参数组合和针对不同煤体结构的测井参数数值,将这些区块按煤岩的镜质组最大反射率平均Ro,max划分为中煤阶区块(0.65%<Ro,max<1.90%)和高煤阶区块(Ro,max>1.90%),基于对前人成果中各测井方法使用情况的统计和对成果中测井参数与煤体结构相关性的分析,探讨不同测井方法在中煤阶煤层和高煤阶煤层的适用性。结果表明:井径测井在中煤阶煤层和高煤阶煤层均适用,自然伽马测井在此2类煤层中均具有参考作用,电阻率测井、声波时差测井和密度测井在此2类煤层中的应用效果差别较大,补偿中子测井在2类煤阶煤层均不适用;因中煤阶煤岩与高煤阶煤岩力学强度差异造成其对外力的变形差异和不同测井参数的敏感性差异,导致不同测井方法对不同煤阶煤层的适用性存在差异。在中煤阶煤层煤体结构识别中,建议以井径测井和电阻率测井作为主要识别方法,以声波时差测井和自然伽马测井作为次要识别方法;在高煤阶煤层煤体结构识别中,建议以井径测井、自然伽马测井和密度测井作为主要识别方法。

Coal structure has an important influence on permeability of coal reservoirs,and permeability is a core parameter in coalbed methane exploration and development.Logging method has been applied in coal body structure identification in a large number of coalbed methane blocks,but it is still in the exploratory stage.This paper systematically collects the logging parameter combinations used by the predecessors in the identification of coal structure in different coalbed methane blocks and the logging parameters for different coal structures.The blocks are divided into medium rank coal blocks(0.65%<Ro,max<1.90%)and high rank coal blocks(Ro,max>1.90%)according to average Ro,maxof the coal rock,based on the statistics on the use of logging methods in previous achievements and the observation of the relativity between logging data and coal body structure in the results,and the applicability of different logging methods in medium coal seam and high coal rank coal seam is discussed.The study found that:Caliper logging and Gamma-ray logging are applicable to both medium and high rank coal seams.Natural gamma logging has reference functions in both medium coal seam and high coal rank coal seams,resistivity logging,sonic time difference logging and density logging differ in the use of medium coal rank coal seams and high coal rank coal seams.Compensated neutron logging is not applicable in both types of coal rank coal seams;Due to the difference of mechanical strength between medium rank coal rock and high rank coal rock,the difference in deformation of external forces and the sensitivity difference of different logging parameters lead to differences in the applicability of different logging methods to different coal ranks.It is suggested that caliper logging and resistivity logging be the main identification methods,with the acoustic travel time logging and Gammaray logging as the secondary identification methods in medium rank seams;it is also suggested that caliper logging,natural gamma logging and density logging be the main identification methods in high rank seams.